Any athlete who uses a principal piece of equipment to compete could likely profit from knowing how the equipment behaves during use and how his/her actions influence the equipment. For example, tennis rackets, guns, helmets, gloves, cleats, shot puts, bobsleds, skis, snowboards, skates, swords, balls of all types, javelins, starting blocks, bicycle tires, bicycle seats, boats, oars, paddles, and many other objects are used by athletes in order to compete. Most athletes spend enormous amounts of money on training and competition equipment. Simply instrumenting a kayak paddle and then testing an athlete with it will not duplicate the actions of the athlete using his/her own paddle. Not only is the size of the equipment important, but the elasticity, mass distribution, padding, and even the sound the equipment makes can influence an athlete's performance. Most elite athletes have a jaundiced view of trying to perform a well-learned skill for a scientist that uses equipment to which they are unaccustomed. Therefore, athletes are tested with their own bikes, boats, canoes, boats, bows, guns, skis, poles, skates, helmets, and so forth (Fig. 2).
The net result is that the idiosyncratic nature of the sport and the athlete's equipment must be preserved while testing is performed. The athlete must use his/her skis, skates, paddle, gloves, and so forth. This puts a premium on designing small sensors that can be attached to the athlete's gear while remaining nearly invisible and weightless; not to mention that the instrument needs to measure the variable of interest. Vision-testing equipment is particularly delicate when used in actual play and must not endanger the athlete's eyes if the equipment is struck.
Simulators have been designed for athlete performance practice and measurement for some time. Rowers are fond of criticizing ergometer measurements because the ergometer ‘does not float’. Simulators have continued to improve in their realism, but are often astonishingly expensive and difficult to develop and implement. Nearly any perceived flaw by the athletes may bring the entire project to a halt because they ‘do not trust it’.
These types of instrumentation are very often custom built and require extraordinary engineering know how. While many brilliant approaches have been used, the time involved and expense often compromise the intended benefits.